# Metabolic reprogramming and gut microbiota ecology drive divergent Plasmodium vivax infection outcomes in Anopheles darlingi

## TL;DR

The study shows how mosquito metabolism and gut bacteria influence whether Anopheles darlingi mosquitoes become infected with Plasmodium vivax malaria parasites.

## Contribution

The study reveals that early metabolic and microbial changes in mosquitoes, triggered by bloodmeal components, determine Plasmodium vivax infection outcomes.

## Key findings

- Low-infection mosquitoes showed early metabolic responses and specific gut bacteria linked to parasite resistance.
- High-infection mosquitoes had limited metabolic changes and bacteria associated with weakened defenses.
- Bloodmeal components act as early conditioning factors influencing mosquito susceptibility to infection.

## Abstract

Anopheles darlingi is the principal malaria vector in the Amazon basin, where Plasmodium vivax accounts for the majority of cases. Despite its epidemiological importance, the molecular and microbial determinants of A. darlingi susceptibility to P. vivax remain poorly understood. Here, we investigated vector-parasite-microbiota interactions using experimental infections with field-derived P. vivax gametocytaemic blood, which produced two distinct infection phenotypes: low and high oocyst burdens. Transcriptomic profiling of mosquito midguts across key parasite developmental timepoints revealed that low-infection mosquitoes mounted an early and sustained response characterised by activation of detoxification pathways, redox regulation, aromatic amino acid catabolism, and purine depletion, likely coordinated through neurophysiological cues, which collectively create a metabolically restrictive environment for parasite development. These physiological changes were accompanied by reduced bacterial diversity and enrichment of Enterobacteriales and Pseudomonadales, taxa previously linked to anti-Plasmodium activity. Conversely, high-infection mosquitoes exhibited limited metabolic reprogramming, expansion of Flavobacteriales, and transcriptional signatures consistent with permissive physiological states, potentially associated with reproductive trade-offs. Importantly, low infection outcomes consistently arose from bloodmeals with the lowest gametocyte densities, suggesting that host- and parasite-derived components of the bloodmeal act as early conditioning factors that prime the mosquito midgut for either resistance or susceptibility. These findings reframe A. darlingi vector competence to P. vivax not as a fixed immune trait but as a dynamic outcome of early redox, metabolic, and microbial interactions. They also highlight ecological and physiological targets for transmission-blocking strategies and reinforce the importance of studying vector-parasite interactions in regionally relevant systems.

Malaria, a parasitic disease transmitted by mosquitoes, relies on complex interactions between the mosquito, the malaria parasite, and microbes that live in the mosquito gut. In the Amazon basin, Anopheles darlingi is the main mosquito that spreads Plasmodium vivax malaria, yet little is known about what makes some mosquitoes more susceptible to parasite infection than others. In this study, we infected A. darlingi with blood from malaria patients from Peru and found that they consistently developed two very different outcomes: some had heavy infections, while others carried very few parasites. By analysing changes in mosquito gene activity and gut bacteria over time, we discovered that mosquitoes with low infection levels triggered early metabolic responses that altered their gut environment, making it hostile to the parasite. These same mosquitoes also carried specific bacterial communities previously linked to parasite resistance. In contrast, mosquitoes with heavy infections showed weaker metabolic changes and had bacteria known to dampen gut defenses. Our findings reveal that malaria transmission success depends not only on the parasite or mosquito immune system, but also on how the bloodmeal reshapes mosquito metabolism and microbiota ecology in the hours after feeding.